


Christmas sin

by Lady_Flame96



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell (Undertale), Christmas Party, Ecto-Genitalia (Undertale), F/F, F/M, I was horny and bored, Lime, M/M, Mom please don't read this!, No Smut, Swapfell Papyrus (Undertale), Swapfell Sans (Undertale), never a good combination, suggestive stuff
Language: English
Status: Completed
Published: 2019-10-18
Updated: 2019-10-18
Packaged: 2020-12-31 05:03:01
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,113
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21079217
Author URL: https://archiveofourown.org/users/Lady_Flame96/pseuds/Lady_Flame96
Summary: You decide to host a nice christmas party... too bad Sans have others plans.You can consider this my only enter for KinkTober/SmutTober.





	Christmas sin

**Author's Note:**

> This was inspired by a nice chapter of a nice story... my weird brain decided to rethink a funny detail in a perverted way.

This Christmas party was going to be perfect! 

You had everything ready! 

Decorations? Check! 

Food? Check! 

The kiss-maker? In position and ready to strike! 

Some people would think that hosting a party with many scary monsters it's a terrible idea, but you know better!

After spending so much time with them (especially with a couple of brothers) you know that they're all sweethearts or Big tsunderes at worst. 

Another reason why this party was going to be amazing was thanks to Chara's idea. When she told to the monsters about the "Ugly Christmas Sweaters" they loved the idea!

So now you're talking and having fun surrounded by weird-reindeers, sweaters with Christmas lights on (Seriously Rus?! Where does he even finds these?!) and horrible puns sewed in the tick material. 

As for you, you actually couldn't choose between two.   
You saw them at different times in different stores but at soon as your eyes landed on them you just had to buy them!

One was long and green (it almost covered your butt) with an upside down Santa stuck in a chimney with his cheeks and two little boots in the air. 

The other was black (very un-christmasy) with little white snowflakes and skulls everywhere, making you think about your skele-bae.

In the end you wore the black one. 

People can make fun of your relationship with the brothers, you don't care!

Speaking of which, you haden't spotted Sans yet... weird...

Was he planning something? 

It was only later, while you were caught up in a conversation with Undyne and Asgore, that you spotted him.

He was just chatting with Alphys and he looked so... peaceful. 

Until you got a better look at him.

Was he...? No, it's impossible! Could he...? Did he...?

Oh

My

Stars!

He was!

He was wearing your green sweater! 

It looked almost like a dress on him! It was covering his pelvis but...

Oh no! He noticed you looking at him!

He observed you for a few seconds before grinning at you with a shark like smile.

Oh my Gosh! That smile!   
He had more up his sleeve! What was he-

Your thoughts were cut short when he excused himself from Alphys and reached down to take something from the floor and-

.

.

.

Wh- wh- what?! W-wh- Why?! 

Why was he not wearing pants?!

You were just there. Frozen in place looking at his (thanks the Stars) empty pelvis. 

(Before meeting the two skeletons you would have never though that bones could be so sexy)

Then he slowly turned his head and sent you a look. A look that sent shivers down your spine.

That little! 

He was teasing you! 

Fine! Two can play this game! If you just ignored him for the rest of the night he'll just drop it. 

Easier said than done! 

You tried to focus on the conversation but he seemed to be everywhere and where he wasn't there was Papyrus, looking at you with a knowing smirk that made you blush and look away making your eyes land where Sans was "casually" standing! 

You could have died of sexual frustration right there if it wasn't for Chara! Your little saviour asked your help with their plan to make Asgore and Toriel kiss under a conveniently placed mistletoe. 

But you weren't done with Sans!

When the party finally ended Chara was sleeping in the arms of a blushing goat man who left with the ex-queen (Yes, the plan worked! Too bad the kid was already asleep when it happened) while Alphys made a comment about unwrapping a super special present to an excessively flustered Undyne. 

Papyrus teleported somewhere. 

You had the house all for yourselves. 

Time to make your names appear on the naughty list!

You wasted no time and reached the bedroom immediately, slamming the door and, letting Sans no time to talk you bolted to him and started kissing. 

Your tongue immediately invaded his mouth and you had a little fight for dominance that he easily won.

This wasn't the first time you experienced the art of lovemaking and you love when he dominates you but it's always fun to be a tease. 

He took his time exploring every inch of your mouth with his magical tongue (pun intended) that always leaves a weird, pleasurable sensation. 

Meanwhile his hands travelled all over your body earning several moans from you. 

But when you started to trace the shape of his ribcage trough his clothes (something that always made him moan) he pulled away from the kiss with a squeak and then froze, embarrassed. 

His skull was engulfed in a blush so bright, he was illuminating the room.

The Malevolent Sans embarrassed?!? Impossible! Something is really wrong here!

"Sans? Are you alright?"

Of course he's not! 

You quickly examined his body.

From his blushing face that he was trying to hide behind his hands (it could have been cute if you weren't so worried) and down

Down 

Down

Down to his pelvis and his... lack of bulge...

Wha- Weren't you- H-he wasn't turned on? Did- Have you done something wrong? Maybe you weren't enough anymore? 

"S-Sorry."

Your self-doubt was interrupted by Sans' voice (gosh he sounded so humiliated!)

"Did I did something wrong?"

"N-No Dearest! You Were Absolutely Perfect! I Just... Made The Wrong Parts."

Oh...

Right... 

You remember THE TALK they, mostly Papyrus, gave you about sex and how they can create either male or female genitalia ("i can try to make them at the same time if you're into that sweet thing" Papyrus told you once with a smirk)

Was he more comfortable having female parts?   
Did he tough that you wouldn't like that and reject him?   
Or, even worst, judge him?!  
(Stars know how many problems they still have with that!)

"Sans, it's not a problem if you feel more comfortable with-"

"IS NOT THAT!" He cuts you off "IS Just... Something That Happens... Sometimes... To Me."

"Do you want to keep going or..?"

"No! Please. Can We Just... Cuddle And Call It A Night?"

His amount of cuteness in this moment makes you smile but you frowned a little on the inside because he still sounds so scared of looking weak or to ask for intimacy. 

"Of course! I would never deny something to you! Besides, Santa's butt kinda ruined the moment."

You both laughter at your weak attempt to lighten the mood.

You got comfortable in the bed and snuggle with each other under the tick covers.

The cold can't reach you and the warmth you feel isn't only physical but it starts from your soul and it spreads trough your bodies with affection. 

This is truly the most beautiful gift.

**Author's Note:**

> First time trying to write sexy stuff.
> 
> The first one who guess which story inspired this wins... I don't know a drawing?
> 
> I have a Tumblr: https://ladyflame-ask.tumblr.com/


End file.
